*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

.container{
    width: 1200px;
    margin:auto;
}

.container::after{
    content:"";
    display: table;
    clear: both;
}

.col{
    float: left;
    width: 33.333333%;
    height: 100px;
    background: orange;
}

/*响应式代码*/
@media (max-width:600px) {
    .container{
        width: 100%;
    }
    .col{
        width: 100%;
    }
}
